In recent years, there has been a notable interest in bio-based and/or biodegradable materials for use in food packaging, agriculture, medicine, and other areas. For example, the poly lactic acid (PLA) made from corn starch by NatureWorks LLC, has been used to produce environmentally friendly products, like International Paper's ECOTAINER. The limited thermal and mechanical properties of virgin biopolymers, however, become the restriction of its applications. Petroleum chemicals, for example, PET, polypropylene, could be added into PLA to improve its performance. By combining Biopolymers, and/or biodegradable polymers, and/or natural fillers, and/or performance promoters or modifiers, we can have better products, while retain good sustainability. The Biopolymers are, but not limit to, PLA, PHA (polyhydroxyalkanoates), cellulose esters, polysaccharides, and so on. The performance promoters or modifiers here are, but not limit to, low molecule weight additives, like catalysts, crosslink agents, tie-agents, plasticizers, stabilizers, nucleating agents, some other polymers, and so on.
PLA is a biodegradable polymer that made from corn starch. Adding petroleum chemicals into PLA could improve the thermal and mechanical performance, but damages the sustainability of the products. By making PLA/biomaterial blends/composites, we can have better products, while retain their sustainability. The biomaterials here are, but not limited to, biopolymers, like PHAs; natural fillers, like cellulose fibers and powders; agriculture (for examples, rice husk, wheat bran, straw, corn cob . . . ) fibers and powders; wood fibers and powders; and bamboo fibers and powders.
Polylactic acid (PLA) is increasing in favor with consumers of plastic thermoformed articles as a renewable plastic which does not derive from fossil fuels and which is degradable in the environment. As with many thermoplastics, PLA has a decreasing mechanical strength with increasing temperature. At higher temperatures approaching about 140° F. (60° C.), an article formed from PLA may lose the ability to resist deformation by forces frequently found in transportation. At temperatures above about 140° F. (60° C.), PLA may lose its ability to resist deformation to forces of the order of magnitude of gravity and residual mold stress. Prolonged exposure of PLA articles to temperatures of about 140° F. (60° C.) or higher may cause these articles to deform substantially from their original shape under forces which may be present in storage conditions. Since temperatures of about 130° F. (54.4° C.) may be exceeded in railcars and trailers used for distribution, PLA articles may suffer from high damage losses during transport through and storage in hot areas such as tractor trailers crossing, for example, the hot weather areas of the United States during the summer season.
Accordingly, it would be desirable to produce PHAs-PLA blends containing articles which have greater resistance to deformation at higher temperatures that may occur during, for example, storage and transportation in hot summer time periods. The composites could be processed on the currently commercial plastic arts production line.